1. Field of the Invention
The present invention relates to a high-frequency module defined by combining a plurality of devices including an antenna, and more particularly, to a high-frequency module having a structure in which a substrate provided with an antenna and another substrate provided with a high-frequency device are joined together.
2. Description of the Related Art
To reduce the size of communication equipment, such as mobile phones, various types of high-frequency modules defined by combining a plurality of devices including an antenna are used.
For example, Japanese Unexamined Patent Application Publication No. 2005-19649 discloses a high-frequency module illustrated in FIG. 12.
Referring to FIG. 12, a high-frequency module 101 has a laminated structure including a first dielectric substrate 103 having an antenna conductor 102 on an upper surface thereof, and a second dielectric substrate 104 having a recessed portion 104a in a lower surface thereof. A high-frequency device 105 and an antenna-characteristic measuring connector 106 are disposed in the recessed portion 104a. 
A ground conductor 107 connected to a ground potential is disposed under substantially the entire lower surface of the first dielectric substrate 103. The ground conductor 107 has a through hole through which a through hole conductor 108 extends so as not to come into contact with the ground conductor 107. An upper end and a lower end of the through hole conductor 108 are connected to the antenna conductor 102 and the antenna-characteristic measuring connector 106, respectively.
In the high-frequency module 101, a terminal electrode 109 is disposed in a lower surface of a frame portion around the recessed portion 104a of the second dielectric substrate 104. The terminal electrode 109 is connected to a high-frequency circuit including the high-frequency device 105. Also, the terminal electrode 109 is connected to an electrode land 111 on a mounting board 110, with a conductive joining member 112 interposed between the terminal electrode 109 and the electrode land 111.
In the high-frequency module 101, the antenna-characteristic measuring connector 106 is disposed in the recessed portion 104a in the lower surface of the second dielectric substrate 104. Since the antenna-characteristic measuring connector 106 is disposed below the ground conductor 107, electromagnetic fields radiated from the antenna are not transmitted to the measuring probe. Therefore, Japanese Unexamined Patent Application Publication No. 2005-19649 states that it is possible to measure the antenna characteristics that are unaffected by the electromagnetic fields.
In the high-frequency module 101, the first dielectric substrate 103 having the antenna conductor 102 on the upper surface thereof and the second dielectric substrate 104 having the high-frequency device 105 on the lower surface thereof are directly stacked together to define an integrated unit.
At the same time, since the intensity of the radio waves radiated from the antenna including the antenna conductor 102 is relatively high, the radio waves propagate from above the antenna conductor 102 to the high-frequency circuit including the high-frequency device 105. Therefore, although the antenna conductor 102 and the high-frequency device 105 are separated from each other by the ground conductor 107, the radio waves from the antenna conductor 102 cause fluctuations in the characteristics of the high-frequency circuit including the high-frequency device 105. That is, although the ground conductor 107 is disposed above the high-frequency circuit including the high-frequency device 105, there is a tendency that radio waves from the antenna conductor 102 are partially transmitted around the ground conductor 107 and affect the high-frequency circuit including the high-frequency device 105.